"The essential question in this case, then, is whether such unions [opposite-sex marriages] possess distinguishing characteristics that are relevant to marriage," they write. "This is not a hard question. Indeed, because of the distinguishing procreative characteristics of heterosexual relationships, until quite recently 'it was an accepted truth for almost everyone who ever lived, in any society in which marriage existed, that there could be marriages only between participants of different sex.'"

"Nowhere in its 136-page opinion does the district court even cite any of the evidence overwhelmingly acknowledging responsible procreation and child-rearing as the animating purpose of marriage," the brief reads.

In his original ruling, Walker dismissed the procreation argument.

"Blankenhorn's [a major witness for the defense] reliance on biology is unsupported by evidence, and the court therefore rejects his conclusion that a biological link between parents and children influences children's outcomes," he wrote.

Supporters of same-sex marriage have thirty days to file a brief in response.

Also last week, a third party requested authority to file an amicus brief arguing against gay marriage. The request, filed by a man named Robert Wooten who describes himself as a California citizen, makes hay of Walker's supposed sexual orientation. Although many same-sex marriage opponents have suggested publicly that, because Walker may be gay, he is biased in the Prop 8 case, none made the argument in court.

The ability of same-sex marriage opponents to pursue an appeal to the ruling is still somewhat up in the air. Walker noted in his initial ruling that, because they weren't the defendants in the original case and because they may not be able to prove any personal harm done by the ruling, they may not be able to appeal. The actual defendants -- the State of California, including Gov. Arnold Schwarzenegger and Attorney General Jerry Brown -- support gay marriage and have declined to appeal.